The present invention relates to a closure device and a catheter assembly suitable for transcatheter operations, i.e., operations for closing or repairing endocardiac or vascular defects.
At present, the Fontan operations have been performed as the repair operations of complex cardiac anomalies such as a single ventricle. In this operation, the cardiac function is repaired by employing a single ventricle for the systemic circulation system, and by directly leading the blood from the vein of the systemic circulation system to the pulmonary artery in the pulmonary circulation system. After this operation, however, extreme decrease in cardiac output may occur because of transient ventricular hypofunction or increase in pulmonary vascular resistance, associated with vasospasm or residual peripheral pulmonary arteriostenosis. Thus, it occasionally becomes difficult to perform postperative management.
In order to avoid increase of the pulmonary vascular resistance and decrease of the cardiac output, therefore, it is general practice for the operation to form a small fenestration or perforation of about 4 mm between atria (in most cases, the interatrial septum is made of an artificial membrane) to allow the blood to flow through the small fenestration or perforation. This procedure followed by formation of the small fenestration or perforation is referred to as the Fontan fenestration. The surgical operation is generally carried out as a method of treatment for closing the small fenestration after the Fontan fenestration. As a matter of course, however, this surgical operation is followed by thoracotomy of a patient in addition to the treatment of the affected area, which imposes a burden on the patient. In particular, in case of child patients, this burden is considerably large.
Percutaneous transluminal therapeutic catheterization is known as a noninvasive procedure for repairing endocardial defects. In this procedure, an atrial septal defect is closed by transveneously inserting an intercardiac catheter into the heart, and closing the atrial septal defect with an occlusion device. The first clinical success of this method was reported by King and Mill in 1976. In the method carried out by King et al, closure of the atrial-septal defect is carried out by introducing left and right atrial double umbrellas into an atrium with an insertion tool composed of a core wire and a double-layered catheter coaxially arranged thereon, fitting the umbrellas on the interatrial septum so that the interatrial septum is sandwiched between them, and then combining the umbrellas into one.
However, this method can not be applied to children, especially, to preschool children since it uses a very thick insertion tool and hard umbrellas. To solve this problem, Rashkind investigated miniaturization of the device, developed in 1977 a single umbrella type occlusion plug with hooks, and reported its clinical success in children. However, this procedure has another problem such that the plug may be occasionally caught in an unintended site of the heart because of its hooks. Thus, when once the umbrella was opened in the heart, the umbrella-like member can not be changed in its position or withdrawn from the site, resulting in emergency operation. To overcome such disadvantages, Rashkind further developed an improved occlusion plug comprising two umbrellas united with one another. This plug has widely been put into clinical use for closure of patent ductus arteriosus.
On the other hand, Lock et al developed a clamshell-shaped intraatrial occlusion device and applied for a patent (JP-A 5-237128), which has been modified by additionally providing coil springs for the double umbrella occlusion plug of Rashkind so that a thin interatrial septum is firmly sandwiched between two umbrellas under the action of the coil springs arranged at each middle portion of eight stainless steel frames of the plug.
This occlusion device is so designed as to be firmly fitted on the thin interatrial septum when the two umbrellas members are in close contact with one another under the overlapped conditions. Because of its configuration similar to a clamshell of a bivalve, this device is called a xe2x80x9cclamshell septal occluderxe2x80x9d. In use, the treatment is carried out by introducing an elongated sheath of 11 French thick into the repair site through a femoral vein of a patient. Since this method is applicable to a patient with a weight of more than 8 kg, it has been widely used as a percutaneous transluminal therapeutic transcatheter closure of atrial septal defects.
The closure treatment of the small hole after Fontan fenestration is done with the occlusion plug by percutaneous transluminal therapeutic transcatheterization.
However, in the method of closing the small hole caused by the Fontan fenestration with the occlusion plug of the prior art, adhesion of thrombus may occur because of a large occlusion plate of the plug, resulting in high risk of complications.
Further, if disembarrassment or dislodgement of the occlusion device has taken place, it is difficult to withdraw the occlusion plug because of its shape or size.
The present invention has been made in view of the above-mentioned circumstances and aimed at providing a closure device for transcatheter operations, that is simple in shape, easy to operate, capable of closing a small hole safely and infallibly, easy to withdraw and less likely to cause adhesion of a thrombus. Also, the present invention is aimed at providing a catheter assembly for introducing the closure device into the site of operation.
As the result of assiduous studies for solution of the above problem, the present inventors have conceived an idea of providing a closure membrane with a fixing means of fixing the closure membrane to a tissue wall surrounding a defect aperture, said fixing means exhibiting a shape memory behavior and recovering its memorized shape when heated to the body temperature to sandwich the tissue wall from both sides of the defect aperture between the fixing means and the closure membrane.
In other words, the subject matter of the present invention is directed to an easily foldable closure device for transcatheter operations, comprising: a flat closure member including a closure membrane and a frame for fimbriating a periphery of the membrane; a fixing member for fixing the closure member to a tissue surrounding a defect aperture; and a connecting member fixed at one end to the fixing member and at the other end to the closure member for holding them in close proximity to one another. The frame, fixing member and connecting member are respectively made of the same or different shape-memory alloys with a shape recovery temperature of 30 to 37xc2x0 C.
According to the present invention, there is provided a closure device for transcatheter operations, comprising: a flat closure member including a closure membrane made of a fabric or non-woven fabric of a bio-compatible material, and a fringing frame for fimbriating or bordering a periphery of said closure membrane, said fringing frame being made of a shape-memory alloy with a shape recovery temperature of 30 to 37xc2x0 C.; a fixing member for fixing said closure member to a tissue surrounding a defect aperture, said fixing member being approximately parallel to one plane of said closure member and adapted to be located on one side of said defect aperture so that said tissue is sandwiched between said fixing member and said closure member located on the opposite side of said defect aperture, said fixing member being made of a shape-memory alloy with a shape recovery temperature of 30 to 37xc2x0 C.; and a connecting member fixed at one end to said fixing member and at the other end to the above-mentioned closure member for holding said closure member and fixing member in close proximity to one another, said connecting member being made of a shape-memory alloy with a shape recovery temperature of 30 to 37xc2x0 C., said closure device being easily foldable at a temperature lower than the shape recovery temperature of said shape memory alloys.
In an embodiment of the present invention, the fringing frame, the fixing member and the connecting member may be formed in one united body. In this case, it is preferred to cover a joint portion of the connecting member and the fringing frame with a tubular covering member to prevent the fixing member from reversing its course.
Further, a base of the fixing member may be stitched to the closure membrane of the closure member with a thread so that the defect aperture is located in the central portion of the closure member when the defect aperture is closed.
In addition, the closure member may be provided with a grappling hole to make it easy to hold the closure device by the holding means of the catheter assembly.
According to the invention, there is also provided a catheter assembly for use in combination with the occlusion device refined as above, comprising a sheath opened at both ends and being able to accommodate a folded closure device, of an operating rod provided at a distal end thereof with a holding means for releasably holding said closure device is provided. The said operating rod is being insertable into sheath from one end thereof under conditions of holding said closure device and being able to unsheathe said closure device through the opposite end of said sheath.
In an embodiment of the present invention, it is preferred to constitute the holding means with an easily flexible linear member extending from the distal end of the operating rod in the axial direction thereof.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.